1. Field of the invention:
The invention is directed to large trucks equipped with air brakes and in particular to the ones having a parking brake valve adapted to be operated with a knob in the driver's cabin. Such valve can control the spring brake of a tractor pulling a trailer and can also, when needed, apply both tractor and trailer parking brakes. The brakes are applied by depressing the knob. The invention consists in locking that knob in the "applied brake" position.
2. Prior art:
No patent appears to correspond to the structure and the purpose of the present invention.
Canadian Pat. No. 1,122,026 discloses a key-operated device including a cylindrical body having a cylindrical recess. A key formed with lugs are adapted to have access to the recess and to rotate a cylindrical member and spindle.
U.S. Pat. Nos. 4,226,103 to Menzie and 4,325,237 to Strickland are directed to locks used on a glad hand brake line coupler. Menzie uses a cylindrical lock with locking fingers but requires no sleeve member around the lock to prevent the depressing of a knob. Stickland uses a lock barrel mechanism extending through a tongue and a tongue receiving recess forming the coupler. The lock barrel has no finger projecting on its periphery and no sleeve to prevent its axial retraction.